Radioimmune assays and enzyme-linked immunosorbent assay (ELISA) were developed for Herpes I and II, CMV, EBV, and Varicella viruses all of which cause chronic viral infections in humans. With these sensitive assay systems available, changes in the immune response to these viruses can be easily determined. Detection of EBV soluble antigen by ELISA is 16 times more sensitive than the conventional CF test. Two of 16 patients with Guillain-Barre syndrome had a simultaneous primary EBV infection. Only one viral isolation (Rubella) was obtained from peripheral blood lymphocytes of patients with Guillain-Barre syndrome. In a patient receiving bone marrow transplantation, Epstein-Barr virus was transferred from the donor and EBNA positive cell lines were established from both donor and recipient. BIBLIOGRAPHIC REFERENCE: Wallen, W. C., Mattson, J. M. and Levine, P. H.: Detection of EBV soluble antigens by ELISA. J. Inf. Diseases (In press), Sept. 1977.